This application relates to methods of constructing water cooling towers, with particular embodiments related to the use of concrete masonry units (CMUs).
Water cooling towers are well known, and are a common heat-exchange component in large commercial, medical, and industrial HVAC systems, in cooling for industrial processes, and aeration of water for other purposes. Cooling towers are a standard part of new construction of buildings or campuses of buildings. Many existing buildings also need replacement or supplemental cooling towers because of the inadequacy of present cooling towers due to increased demands, higher temperatures, consolidation into campus-wide HVAC systems, or deteriorating performance of existing cooling towers.
An under-performing cooling tower can be a large problem for commercial properties, medical facilities, and industries, affecting the efficiency and therefore the operating costs of HVAC and industrial systems, and affecting the comfort and therefore the satisfaction, health, and productivity of persons. Under such circumstances, existing cooling towers need to either be replaced or be supplemented with new cooling towers. But replacement requires taking an existing cooling tower out of service and waiting for the construction of a new cooling tower to be completed. And supplementation requires finding a new location for the new cooling tower, and then waiting for its construction to be completed.
One common type of industrial cooling tower is a counterflow tower where water falls by gravity through fill media from water nozzles positioned in the upper part of the cooling tower. A water collector pan is positioned below the fill layer. The water is directed to a downstream water basin, from where it is re-circulated back into the spraying nozzles on top. A source of moving air is mounted on or in the cooling tower, directing the cooling air toward the water.
Cooling towers exploit the evaporative cooling of water exposed to air. Therefore they are generally located outside. Cooling towers must provide a very large surface area for water to interact with air. Therefore cooling towers are often very large structures—with one example being at least a 20-square-foot footprint and at least 10 feet of height—and some towers being many times that large. Powerful motorized fans are generally required to provide adequate air flow. Water is heavy, and powerful fans are heavy, and therefore cooling towers are heavy structures when in use, and the basic structure of the cooling tower must be capable of withstanding the internal forces of the heavy moving water and heavy moving fan, and the external forces of the outside environment.
Cooling towers are typically located outside, take up a lot of space, can be noisy, and may generate mist or vapor. They are typically placed on the roofs of high-rise buildings or in otherwise out-of-the-way locations on the grounds or the campus. Such locations present problems in the construction and installation of cooling towers. A heavy crane might be necessary—for months—in order to lift construction materials or pump concrete onto a rooftop or into an inaccessible area at ground level. There might be very little adjacent “laydown” or staging area for construction crews, materials, and equipment.
Industrial cooling towers made of wood in the traditional way are susceptible to fire and to rot and early deterioration in the constantly wet cooling-tower environment, requiring proper preparation and constant maintenance throughout the operational life of the cooling tower.
Cooling towers made of steel are known, but are very expensive, very heavy to transport and erect, and require highly skilled workers in the design phase, any pre-fabrication phase, and in the erecting or construction phase, in order to avoid potential failure, improper fitting of components, or even injury to persons and property. Also, steel is subject to rusting and deteriorating in the constantly wet environment if it is not properly prepared and constantly maintained throughout the operational life of the cooling tower.
Cast-concrete cooling towers can be built using the shuttering method, where sections of the framework are built using wooden forms; then concrete is poured into the forms to make a first lateral row. After the concrete sets, the next lateral layer is formed, filled with concrete, and allowed to set. This process continues until the structure reaches the desired height. The construction of such a tower is a major undertaking requiring many months, even a year, to complete. The logistics and heavy equipment required are extensive. Such traditional towers have underground basins and require extensive engineering and design in advance of construction.
Fordyce and Fritz (U.S. Pat. No. 3,834,681 A) teach an open-frame, prefabricated, concrete cooling tower structure. Furlong, et al. (U.S. Pat. No. 3,917,765 A) teach a cooling tower shell of factory-made pre-cast concrete parts. Curtis (U.S. Pat. No. 5,227,095 A) teaches a cooling tower system consisting of individual modules, which can be built from fiberglass in a factory and then transported to and erected on site. Curtis and Oberlag (U.S. Pat. No. 5,545,356 A) teach a method of constructing a cooling tower structure by casting the concrete walls on site in a horizontal position and then raising the walls to a vertical position—a “tilt-up” construction, or by pre-casting concrete modular wall units off-site and transporting and erecting them on site.
There is some question whether “tilt-up” and some other concrete pre-fabrication methods are capable of producing stable structures generally. For example, concerns about, and even requirements to retrofit, such structures in earthquake-prone areas.
Concrete pre-fabrication, like steel, requires highly skilled workers in the design phase, the pre-fabrication phase, and in the erecting or construction phase, in order to avoid potential failure, improper fitting of components, or even injury to persons and property.
All of the presently known methods of constructing cooling towers have at least one of the disadvantages of being insufficiently durable, too expensive, too difficult to transport, too long to place into operation, too difficult to erect or construct without highly skilled labor and long-term use of heavy machinery, and too difficult to maintain over the operational lifetime of the cooling tower.
Concrete masonry units (CMUs) and proper construction methods and standards for their manufacture and erection are known in other fields of construction. The advantages of CMUs include very low cost, greater strength at lighter weight than cast or pre-cast concrete, and the ability of masons of ordinary skill to quickly build structures according to already well-known methods. In CMU construction, hollow concrete blocks are reinforced with steel rebar or similar material and filled with concrete, mortar, or grout, with construction proceeding layer by layer, continuously, without having to wait for each concrete layer to set.